Feed pump

ABSTRACT

The invention relates to a feed pump for delivering fluid media, wherein the pump bearings are lubricated by the feed medium itself. Connecting channels with valve devices are provided on the suction side and on the pressure side upstream and downstream, respectively, of a displacement element and link the bearing area of the pump with the production channel. Said connecting channels are configured as straight bores in the pump housing. The valve devices are configured as tappets that are disposed in the associated connecting channel sections so as to be displaced while being tight with respect to suction.

[0001] The invention relates to a feed pump for delivering fluid media according to the precharacterizing part of the main claim.

[0002] In many chemical conveyor systems, gear pumps or rotary piston pumps are used to deliver the medium, the lubrication necessary for the plain bearings of the pump taking place through the feed medium itself.

[0003] According to GB 322 78, the medium to be delivered normally has a high fluidity. In the normal operation of the system, there prevails on the suction side of the pump a pressure P1 that is lower than the pressure D2 prevailing on the pressure side of the pump, and through this pressure difference the feed medium is pressed or sucked, as the case may be, over the surfaces of the plain bearings to be lubricated. This actual feed medium acting as the lubricant is released again into the material current on the suction side of the pump, since on the suction side and on the pressure side connecting channels with valve devices are arranged before and after the actual pump, which connecting channels connect the bearing area of the pump to the production channel.

[0004] If, for any production-technology reason, the normal pressure difference between the region before the pump and the region after the pump becomes reversed, i.e. the suction side normally showing a low pressure suddenly shows a higher pressure than the pressure side, which normally shows a higher pressure, it has become known in practice to design the provided valve device as a spring-controlled valve that automatically closes or opens the associated connecting channels depending on the prevailing pressure.

[0005] This reversal of the pressure difference between the region before and after the actual pump always occurs when the region after the pump, for example for production-technology reasons, is for example suddenly opened to the atmosphere, in order to carry out any operation after the pump, for example on the attached production equipment. The spring-controlled valves provided in a known manner operate satisfactorily with low-viscosity, fluid media.

[0006] In the processing of high-viscosity polymer melts, e.g. according to JP 005-052 186 A, such valves cannot be used. In the case of high-viscosity polymer melts, these known, spring-controlled and spring-loaded valves would clog and are thus not functional in these feed media.

[0007] The invention is based on the task of making possible a reversal of the feed media lubricating the plain bearings even with the use of high-viscosity polymer melts, in connection with which a purging of the connecting channel should be simultaneously possible during the delivery of the high-viscosity polymer melt.

[0008] This task forming the basis of the invention is accomplished through the teaching of the main claim.

[0009] An advantageous embodiment is explained in the dependent claim.

[0010] Expressed in other words, it is proposed that, instead of a spring-loaded flap valve or multiple-way valve, valve plungers be used, wherein the connecting channels provided in the pump housing are formed as straight-line bores and the valve tappets completely close these connecting channels, i.e. suction-tight, but are arranged displaceably in these connecting channels. The valve tappets are adapted to these connecting channels not only with respect to the diameter of the bores, but also with respect to the length of the bores; in other words, the valve tappets close off the channels over their entire length.

[0011] Thus, in the closed state, on the one hand the flow of the feed medium is stopped, and on the other hand the bore is simultaneously purged of the polymer material present in it, so that a cracking of this material inside the bore cannot occur.

[0012] The controlling of the valve tappets can take place automatically via pressure sensors, the pressure in the production channel being measured before and after the pump and used to control the valve tappets.

[0013] While in the preceding the invention is explained by considering high-viscosity polymer melts as an example, the arrangement according to the invention can also be applied in the case of general fluid media and in that context replace the known flap valves.

[0014] In the following, an embodiment example of the invention is explained with reference to the drawings. In the drawings:

[0015]FIG. 1 shows an arrangement in which, in the normal manner, a pressure prevails at the suction side of the actual pump that is lower than the pressure prevailing at the pressure side of the pump after the pump, and

[0016]FIG. 2 shows an arrangement in which this pressure difference is reversed.

[0017] In the drawings, indicated with 1 is a pump housing having a pump cover 2 and 2 a. Inside the pump housing is arranged a displacement element 6, for example a gear, which is driven by a drive shaft 4 and supported by plain bearings 10 and 11.

[0018] The displacement element 6 is arranged in a production channel 7 and thus creates a suction side S₁ and a pressure side D₁ in the production channel 7.

[0019] At 10 and 11 can be seen the plain bearings for the drive shaft 4, and the medium flowing or propelled in the production channel 7 is led back again to the production channel through the plain bearings, connecting channels 8 and 8 a being provided on the suction side S₁. The flow of this production medium, which at the same time serves as the lubricant, is indicated by the arrow.

[0020] On the pressure side D₁ of the arrangement, connecting channels 9 and 9 a are likewise provided.

[0021] These connecting channels 8, 8 a; 9, 9 a in the pump housing 1 are formed as straight-line bores and, in the illustrated embodiment example, penetrate the pump housing 1 in its entire height.

[0022] Aligned with the connecting channels 8, 8 a and 9, 9 a, tappets 12, 12 a and 14, 14 a are provided in the pump covers 2, 2 a. For reasons of clarity, the actuation means of the tappets are not shown in the drawings.

[0023] In the arrangement according to FIG. 1, prevailing at the suction side S₁ is a pressure P₁ that is lower than the pressure P₂ that prevails at the pressure side D₁, so that by necessity the medium flowing in the production channel 7 is sucked through the plain bearings 10 and 11 as lubricant and is led back again to the production channel 7 via the connecting channels 8 and 8 a.

[0024] Illustrated in FIG. 1 is the fact that the tappets 14 and 14 a completely close off the associated connecting channels 9 and 9 a.

[0025] In the arrangement according to FIG. 2, a pressure reversal has occurred, i.e. prevailing at the suction side S₂ is a lower pressure P₁ than the pressure P₂ prevailing at the pressure side D₂, and for this reason the tappets 12 and 12 a, controlled by sensors, have closed off the associated connecting channels 8 and 8 a and the tappets 14 and 14 a have been opened, so that the connecting channels 9 and 9 a have thus been opened and from now on the feed medium flowing in the production channel 7 is pushed by the pump through the connecting channels 9 and 9 a according to the drawn arrows.

[0026] Since the tappets 12, 12 a and 14, 14 a, when in their inserted state, in each case completely close off the associated connecting channels 8 and 8 a, 9 and 9 a, during their entry into the associated connecting channels these tappets simultaneously purge these connecting channels, i.e. they push the material possibly present in these connecting channels, namely the high-viscosity polymer melt, from the connecting channel into the production channel and thereby purge this connecting channel. Thus, in addition to the functional reversal of the lubricant flow, there occurs at the same time a complete closing off of the connecting channels, so that a residue of high-viscosity polymer melt in these channels is not possible. 

1. Feed pump for delivering fluid media, wherein the pump bearings are lubricated by the feed media themselves and connecting channels (8, 9; 8 a, 9 a) with valve devices are provided on the suction side as well as on the pressure side of a displacement element (6), i.e. before and after the latter, which connecting channels connect the bearing region of the pump with the production channel (7), characterized in that the connecting channels (8, 9; 8 a, 9 a) are configured in the pump housing (1) as straight-line bores and the valve devices are configured as tappets (12, 12 a; 14, 14 a) that are displaceable and are arranged in a suction-tight manner with respect to the associated connecting channel sections.
 2. Feed pump as claimed in claim 1, characterized in that the tappets (12, 12 a; 14, 14 a) are controllable subject to the pressure prevailing in the production channel (7) before and after the displacement element (6). 